Don't suggest writing a bodyless arm if the pattern can never be a never pattern

compiler/rustc_parse/src/parser/expr.rs

@@ -2937,7 +2937,13 @@ impl<'a> Parser<'a> {
  let is_almost_fat_arrow = TokenKind::FatArrow
  .similar_tokens()
  .is_some_and(|similar_tokens| similar_tokens.contains(&this.token.kind));
- let mut result = if !is_fat_arrow && !is_almost_fat_arrow {
+
+ // this avoids the compiler saying that a `,` or `}` was expected even though
+ // the pattern isn't a never pattern (and thus an arm body is required)
+ let armless = (!is_fat_arrow && !is_almost_fat_arrow && pat.could_be_never_pattern())
+ || matches!(this.token.kind, token::Comma | token::CloseDelim(Delimiter::Brace));
+
+ let mut result = if armless {
  // A pattern without a body, allowed for never patterns.
  arm_body = None;
  this.expect_one_of(&[token::Comma], &[token::CloseDelim(Delimiter::Brace)]).map(

tests/ui/half-open-range-patterns/range_pat_interactions1.rs

@@ -17,7 +17,7 @@ fn main() {
  }
  match x as i32 {
  0..5+1 => errors_only.push(x),
- //~^ error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `+`
+ //~^ error: expected one of `=>`, `if`, or `|`, found `+`
  1 | -3..0 => first_or.push(x),
  y @ (0..5 | 6) => or_two.push(y),
  y @ 0..const { 5 + 1 } => assert_eq!(y, 5),

tests/ui/half-open-range-patterns/range_pat_interactions1.stderr

@@ -1,8 +1,8 @@
-error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `+`
+error: expected one of `=>`, `if`, or `|`, found `+`
  --> $DIR/range_pat_interactions1.rs:19:17
  |
 LL | 0..5+1 => errors_only.push(x),
- | ^ expected one of `,`, `=>`, `if`, `|`, or `}`
+ | ^ expected one of `=>`, `if`, or `|`
 
 error[E0408]: variable `n` is not bound in all patterns
  --> $DIR/range_pat_interactions1.rs:10:25

tests/ui/half-open-range-patterns/range_pat_interactions2.rs

@@ -9,7 +9,7 @@ fn main() {
  match x as i32 {
  0..=(5+1) => errors_only.push(x),
  //~^ error: inclusive range with no end
- //~| error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `(`
+ //~| error: expected one of `=>`, `if`, or `|`, found `(`
  1 | -3..0 => first_or.push(x),
  y @ (0..5 | 6) => or_two.push(y),
  y @ 0..const { 5 + 1 } => assert_eq!(y, 5),

tests/ui/half-open-range-patterns/range_pat_interactions2.stderr

@@ -6,11 +6,11 @@ LL | 0..=(5+1) => errors_only.push(x),
  |
  = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
-error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `(`
+error: expected one of `=>`, `if`, or `|`, found `(`
  --> $DIR/range_pat_interactions2.rs:10:17
  |
 LL | 0..=(5+1) => errors_only.push(x),
- | ^ expected one of `,`, `=>`, `if`, `|`, or `}`
+ | ^ expected one of `=>`, `if`, or `|`
 
 error: aborting due to 2 previous errors
 

tests/ui/parser/attribute/attr-stmt-expr-attr-bad.rs

@@ -84,15 +84,15 @@ fn main() {}
 
 #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] 10 => () } }
 //~^ ERROR inclusive range with no end
-//~| ERROR expected one of `,`, `=>`, `if`, `|`, or `}`, found `#`
+//~| ERROR expected one of `=>`, `if`, or `|`, found `#`
 #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] -10 => () } }
 //~^ ERROR inclusive range with no end
-//~| ERROR expected one of `,`, `=>`, `if`, `|`, or `}`, found `#`
+//~| ERROR expected one of `=>`, `if`, or `|`, found `#`
 #[cfg(FALSE)] fn e() { match 0 { 0..=-#[attr] 10 => () } }
 //~^ ERROR unexpected token: `#`
 #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] FOO => () } }
 //~^ ERROR inclusive range with no end
-//~| ERROR expected one of `,`, `=>`, `if`, `|`, or `}`, found `#`
+//~| ERROR expected one of `=>`, `if`, or `|`, found `#`
 
 #[cfg(FALSE)] fn e() { let _ = x.#![attr]foo(); }
 //~^ ERROR unexpected token: `#`

tests/ui/parser/attribute/attr-stmt-expr-attr-bad.stderr

@@ -365,11 +365,11 @@ LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] 10 => () } }
  |
  = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
-error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `#`
+error: expected one of `=>`, `if`, or `|`, found `#`
  --> $DIR/attr-stmt-expr-attr-bad.rs:85:38
  |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] 10 => () } }
- | ^ expected one of `,`, `=>`, `if`, `|`, or `}`
+ | ^ expected one of `=>`, `if`, or `|`
 
 error[E0586]: inclusive range with no end
  --> $DIR/attr-stmt-expr-attr-bad.rs:88:35
@@ -379,11 +379,11 @@ LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] -10 => () } }
  |
  = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
-error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `#`
+error: expected one of `=>`, `if`, or `|`, found `#`
  --> $DIR/attr-stmt-expr-attr-bad.rs:88:38
  |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] -10 => () } }
- | ^ expected one of `,`, `=>`, `if`, `|`, or `}`
+ | ^ expected one of `=>`, `if`, or `|`
 
 error: unexpected token: `#`
  --> $DIR/attr-stmt-expr-attr-bad.rs:91:39
@@ -399,11 +399,11 @@ LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] FOO => () } }
  |
  = note: inclusive ranges must be bounded at the end (`..=b` or `a..=b`)
 
-error: expected one of `,`, `=>`, `if`, `|`, or `}`, found `#`
+error: expected one of `=>`, `if`, or `|`, found `#`
  --> $DIR/attr-stmt-expr-attr-bad.rs:93:38
  |
 LL | #[cfg(FALSE)] fn e() { match 0 { 0..=#[attr] FOO => () } }
- | ^ expected one of `,`, `=>`, `if`, `|`, or `}`
+ | ^ expected one of `=>`, `if`, or `|`
 
 error: unexpected token: `#`
  --> $DIR/attr-stmt-expr-attr-bad.rs:97:34

tests/ui/parser/issues/issue-24375.rs

@@ -3,7 +3,7 @@ static tmp : [&'static str; 2] = ["hello", "he"];
 fn main() {
  let z = "hello";
  match z {
- tmp[0] => {} //~ ERROR expected one of `,`, `=>`, `@`, `if`, `|`, or `}`, found `[`
+ tmp[0] => {} //~ ERROR expected one of `=>`, `@`, `if`, or `|`, found `[`
  _ => {}
  }
 }

tests/ui/parser/issues/issue-24375.stderr

@@ -1,8 +1,8 @@
-error: expected one of `,`, `=>`, `@`, `if`, `|`, or `}`, found `[`
+error: expected one of `=>`, `@`, `if`, or `|`, found `[`
  --> $DIR/issue-24375.rs:6:12
  |
 LL | tmp[0] => {}
- | ^ expected one of `,`, `=>`, `@`, `if`, `|`, or `}`
+ | ^ expected one of `=>`, `@`, `if`, or `|`
 
 error: aborting due to 1 previous error
 

tests/ui/parser/match-arm-without-body.stderr

@@ -1,8 +1,8 @@
-error: expected one of `,`, `=>`, `if`, `|`, or `}`, found reserved identifier `_`
+error: expected one of `=>`, `if`, or `|`, found reserved identifier `_`
  --> $DIR/match-arm-without-body.rs:13:9
  |
 LL | Some(_)
- | - expected one of `,`, `=>`, `if`, `|`, or `}`
+ | - expected one of `=>`, `if`, or `|`
 LL | _ => {}
  | ^ unexpected token
 
@@ -44,11 +44,11 @@ LL +
 LL ~ _ => {}
  |
 
-error: expected one of `,`, `.`, `=>`, `?`, `}`, or an operator, found reserved identifier `_`
+error: expected one of `.`, `=>`, `?`, or an operator, found reserved identifier `_`
  --> $DIR/match-arm-without-body.rs:36:9
  |
 LL | Some(_) if true
- | - expected one of `,`, `.`, `=>`, `?`, `}`, or an operator
+ | - expected one of `.`, `=>`, `?`, or an operator
 LL | _ => {}
  | ^ unexpected token
 

tests/ui/parser/pat-lt-bracket-1.rs

@@ -1,7 +1,7 @@
 fn main() {
  match 42 {
  x < 7 => (),
- //~^ error: expected one of `,`, `=>`, `@`, `if`, `|`, or `}`, found `<`
+ //~^ error: expected one of `=>`, `@`, `if`, or `|`, found `<`
  _ => ()
  }
 }

tests/ui/parser/pat-lt-bracket-1.stderr

@@ -1,8 +1,8 @@
-error: expected one of `,`, `=>`, `@`, `if`, `|`, or `}`, found `<`
+error: expected one of `=>`, `@`, `if`, or `|`, found `<`
  --> $DIR/pat-lt-bracket-1.rs:3:7
  |
 LL | x < 7 => (),
- | ^ expected one of `,`, `=>`, `@`, `if`, `|`, or `}`
+ | ^ expected one of `=>`, `@`, `if`, or `|`
 
 error: aborting due to 1 previous error